This invention relates to carriers used in clean room type environments, and more particularly to an apparatus and method for cleaning carriers used in the semiconductor fabrication industry.
The process of forming semi-conductor wafers or other delicate electronic components into useful articles requires high levels of precision and cleanliness. As these article become increasingly complex and miniaturized, contamination concerns increase. Contamination may be introduced to the substrates through the air as well as though handling devices and equipment. Contamination causes lower yield of circuit components and correspondingly increases manufacturing costs.
Airborne contamination is often significantly reduced by providing controlled fabrication environments known as clean rooms. While clean rooms effectively remove airborne contaminants found in ambient air, it is often not possible or advisable to completely process wafers in the same clean room environment. Moreover, not all contaminants are eliminated. For that and other reasons, semi-conductor wafers are transported, stored, and fabricated in bulk with the assistance specialized handling equipment such as protective carriers or pods. These carriers generally include closures that enable the carriers or pods to maintain their own micro-environment. This further reduces the potential contamination from some airborne particles.
Contamination and contaminants can be generated and introduced to wafers or substrates through the handling equipment. For example, particulates can be generated mechanically by wafers as they are inserted into and removed from wafer carriers, and as doors are attached and removed from the carriers, or they can be generated chemically in reaction to different processing fluids. Contamination can also be the result of out-gassing on the carrier, biological sources due to human activity, or even the result of improper or incomplete washing of the carrier. Contamination can also accumulate on the exterior of a carrier as the carrier is transported from station to station during processing.
Contamination of the specialized handling equipment can be reduced by periodically washing and/or cleaning of said equipment. U.S. Pat. No. 5,562,113 to Thompson et al., U.S. Pat. No. 5,363,867 to Kawano et al. and U.S. Pat. No. 4,133,340 to Ballard each disclose wafer carrier cleaning apparatuses. Thompson, Kawano and Ballard each employ a single fluid circuit. The fluid used to clean the outer surface of the carrier and the fluid used to clean the inner surface of the carrier are sourced from a common reservoir and drain off the equipment into a common drain.
In operation, the outer surface of the carrier accumulates more contaminants because it is exposed to the environment. The spent cleaning fluids may be recycled during the washing process. However, it is not desirable to introduce such recycled fluids to the interior of the carrier because suspended contaminants from the exterior may contaminate the interior.
The use of a common fluid duct also does not allow the washing apparatus to use different cleaning fluids on the inner and the outer surfaces of the carrier. Different washing fluids are often desired because the outside and inside surface of the wafer container have different cleaning properties. Cleaning apparatuses of the prior art that are capable of using separate fluids for the interior and exterior cannot recycle because the commonly collected spent fluid is a mixture and no longer appropriate for cleaning.
There are several problems associated with the prior art cleaning apparatuses. They use large amounts of cleaning fluids because they do not provide for recycling. Cleaning apparatuses that do recycle are unable to tailor the fluids to the specialized needs of both the exterior and interior surfaces. They also do not provide for the cleaning of accessory items, such as doors or closures.
Therefore, there is a need for a wafer carrier cleaner with minimal cross-contamination between exterior and interior surface cleaning fluids, a wafer carrier cleaner that conserves valuable resources, a wafer carrier cleaner with a door cleaning capability, and a wafer carrier cleaner that can operate in a moderately controlled environment.